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Discussion Starter #1 (Edited)
2005 CDI: Engine or Exhaust noise?

Last December I purchased a CPO 2005 CDI w/ 47K and I love the car. Previously, I had a 1997 300D for five years. The 05' CDI is very quiet (and quick) compared to the 1997 and certainly compared to the old 77-85 diesels (I also had a '78 for a time). However, during normal acceleration from a stop, between 0-1500 RPM, the engine is quite "clattery" until it shifts, but otherwise, emits a almost likeable diesel "purr" while idling or at speeds above 30 MPH. It literally sounds as if something like a bike chain is rubbing against metal. I had test driven other 05's and 06's CDI's, and didn't notice or recall this clatter. Also, the noise is not there (or apparent) while the car is cold and driven for the first 5-10 minutes. So my question is to any '05 or '06 CDI owners: do these engines become louder as they age and/or the miles accumulate? Is there some mechanical reason for this that I should have looked at my MB? Could it be faulty exhaust components? Engine mounts? A worn timing chain (if it indeed has one)? Oil? Any helpful suggestions appreciated.

Thanks
Steve
 

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'71 Pinto
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4,239 Posts
Not directly related to your concern nonetheless if, and when you bring the vehicle in mention the following for precaution:

DTB P-B-07.16/55c – modified EGR valve and modified ECU software. Resolves a number varying of engine performance complaints (i.e.: surging, hesitation, misfiring, etc).

Service Campaign 2006070003 211 MY05-06, VIN range A530155 through A835762 incorrect glow plugs may have been installed during the last workshop visit due to an error in replacement part documentation resulting in poor engine performance.
 

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2005 E320 Sedan
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I'm assuming that your car's still under warranty - why not just ask the dealer?

I've not heard any such complaints from diesel owners. My experience with mercedes engines is that they tend to get quieter with miles...
 

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Discussion Starter #4
I'm assuming that your car's still under warranty - why not just ask the dealer?

I've not heard any such complaints from diesel owners. My experience with mercedes engines is that they tend to get quieter with miles...
Frankly, I don't trust MB dealship . Without a doubt, the reply would be, "this is normal..,they all sound like that...). Another factor is that I am in California, where these 2005-06 CDI vehicles were never sold new here due to the emission laws, etc. Even wtih the 1997 E300 D I previously owned, the MB dealership often complained that they did not "see many of these" and they had to constantly call MB central to diagnose problems. Even with this car, when they recently ordered a fuel filter, there was an additional part specific for a diesel that they didn't order, due to lack of expertise with these cars. I just wanted some insight from others who have had these models with actual experience in owning and/or repairs, something I would not get from a MB dealship here.
Warranty? You bet (CPO). I purchased extra years as I know these cars are quite coslty to repair.
 

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2006 E320 CDI, 2009 ML320 Bluetec, 2009 GL320 Bluetec
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However, during normal acceleration from a stop, between 0-1500 RPM, the engine is quite "clattery" until it shifts, but otherwise, emits a almost likeable diesel "purr" while idling or at speeds above 30 MPH
Acceleration = What? Full throttle, light throttle or something in between.

The reason I ask is the CRI systems can vary the number of injections per combustion stroke depending on load (Load=how far you are pressing the gas pedal)

Under light load the ECU command multiple injections per combustion stroke to soften the "diesel clatter" by way of a more controlled pressure rise in the cylinder. Under full load the ECU regardless of engine rpm injects a single larger shot of fuel in order to maximize the burn time, this can occur at high load or high rpms depending on the injection mapping for various years.

It literally sounds as if something like a bike chain is rubbing against metal.
This is NOT combustion related! You need to find out where that noise is coming from, I would start with the dealer or get a stethoscope and start listening. The CDI does have a timing chain, use of the wrong oil or oils that are not approved under MB229.5 or MB229.51 can lead to timing chain damage and increased wear. Grant it you have low miles BUT there still could be an issue with the chaing. Of course this is based on your description of the sound, not being there to hear it I have to base my opinion on your description of the issue.

Also, the noise is not there (or apparent) while the car is cold and driven for the first 5-10 minutes.
That statement leads me to believe you may have an issue with the internal timing chain tensioner. The tensioner uses engine oil pressure to take up slack in the timing system. Cold engines equate to thicker oil until the engine warms up, and you state the noise is evident after 5-10 minutes after it warms up. Oil at normal operating temperature flows more easily, if the tensioner has wear and higher internal leakage the oil once warm can cause it to not apply the correct amount of tension.

Again it leads back to what type of oil are you using? Is it MB rated for the CDI (229.5 or 229.51)? Viscosity and manufacturer is irrelevant as long as your oil meets those two key certifications. So if you tell us "The engine has synthetic oil" then I will take that to mean Synthetic trailer hitch grease which translates into the wrong oil being installed in your motor. We need specifics in regards to certification because all CDI's madate the use of Sytnethic with appropriate MB certifications.


Could it be faulty exhaust components? Engine mounts?
Exhaust components I would say highly unlikely. Except for the turbine and VNT there are no moving parts in the exhaust system. Heat shields? probable but not likely based on your described observations.

I am inclined to think you may have a bad timing chain tensioner from what I have managed to understand from your post thus far.

DB
 
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